The present invention relates to a vehicle with a forwardly or rearwardly disposed drive unit for a single axle and four wheel drive. More particularly, the present inventionr elates to a vehicle drive unit including a combustion engine, a transmission, and a drive shaft connected to wheel drive differentials, a transfer case or middle differential.
Vehicles with all wheel drive are known (Magazine Auto Motor and Sport, Apr. 20, 1983, pages 4 to 7) in which the forwardly or rearwardly disposed drive unit is rigidly connected to a pipe-like longitudinal support in which a drive shaft leading to the differentials is borne. These vehicles have direct transmission and the transmission is rigidly affixed to the combustion engine and the entire unit is positioned in succession in the longitudinal direction of the vehicle. With respect to vibration, such rigidly coupled connections of the combustion engine and the transmission, on the one hand, and the combustion engine and the support, on the other hand, have the disadvantage that the vibration causing engine creates additional vibrations on the drive units (support, drive shaft, transmission) which leads to increased stresses on the individual units and causes a higher noise level. Because of the rigid connection of all components of the drive unit, special tuning of the drive units, e.g. tuning the combustion engine to lower frequencies with respect to the driving support, is not possible for achieving an improvement in driving comfort.
The known configuration of positioning the combustion engine as an extension of the transmission results in disadvantages with respect to the relatively long length of the structure because a larger structural area is required and a pliable and torsionally strong combination has to be created. Furthermore, the distribution of weight with such a configuration is inefficient with respect to the axial load distribution, particularly in rear engine and all wheel drive vehicles.
An object of the present invention is to create a vehicle of the aforementioned category in which the individual components of the drive unit are isolated from each other with respect to vibration effects and the components of the drive unit can be shifted in location. Furthermore, the individual components of the unit can be of smaller structural length, requiring less area, and affording an optimal distribution of weight. Within certain limits, this design will also enable an adjustable repositioning of the engine, depending upon the structural design of the vehicle.
According to the present invention, an improved vehicle drive unit is provided which isolates all of the individual components with respect to vibration effects. This vibration isolation is accomplished by utilizing numerous elastic bearings and a flexible shaft between the engine and the transmission.
The advantages obtained with the present invention relate to the fact that the vibration de-coupling or isolation of the combustion engine from the other drive units as a result of a separate bearing from the support and the transmission enables an optimal low-frequency tuning of the engine in harmony with the drive unit and the chassis. In addition, a beneficial isolation of the combustion engine from vibrations on the drive unit and on the chassis can be achieved. As a result of this design, a favorable noise level and vibration level can be achieved and this allows for a thinner, and lighter, support.
The engine is connected to the transmission by a transmission shaft which has elastic intermediate elements, such a couplings, to give the shaft low torsional rigidity and to allow it to be pliable. As a result, a variable positioning of the combustion engine with respect to the transmission is possible within limits. For favorable results, the engine can be positioned close to the differential. This configuration also results in an optimal distribution of load on the vehicle axles in such a way that the combustion engine is aligned with the vehicle axle, on the one side, and the clutch, the transmission, and the auxiliary units are aligned with the vehicle axle, on the other side. This configuration on the vehicle axle is particularly advantageous for a rear end positioning of the drive nit.
According to certain preferred embodiments of the present invention the combustion engine, when seen in the direction of travel, is placed in front of the transmission and a rear section of the engine partially covers the transmission housing. This results in a shorter structurallength than in known configurations with rigidly connected engine and transmission which are sequentially arranged, when viewed in the direction of travel.
The de-coupled design of the individual components of the drive unit makes it structurally simpler for placing the auxiliary units in a smaller area which has better drive results. As a result of this design, fewer temperature problems occur near the transmission and away from the semi-encapsulated combustion engine. The clutch, for example, is separated from the engine and placed directly at the gear shift box and the driving or flywheel is at the transmission input, largely preventing transmission vibration.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purpose of illustration only, embodiments in accordance with the present invention.